Abstract [en]

The present study is a part of an effort to understand the mechanism of the oxidative chlorination, as performed by a biomimetic non-heme iron complex. This catalytically active complex is generated from a peroxide and [(TPA)FeIIICl2]+ [TPA is tris(2-pyridylmethyl)amine]. The reaction catalyzed by [(TPA)FeCl2]+/ROOH involves either [(TPA)ClFeV=O]2+ or [(TPA)ClFeIV=O]+ as an intermediate. On the basis of density functional theory the reaction of these two possible catalysts with cyclohexane is investigated. A question addressed is how the competing hydroxylation of the substrate is avoided. It is demon- strated that the high-valent iron complex [(TPA)Cl– FeV=O]2+ is capable of stereospecific alkane chlorination, based on an ionic rather than on a radical pathway. In contrast, the results found for [(TPA)ClFeIV=O]+ cannot explain the experimental findings. In this case the transition states for chlorination and hydroxylation are energetically too close. The exclusive chlorination of the substrate by Cl–FeIV=O may be explained by an indirect or a direct effect, altering the position of the competing rebound barriers.

Noack, Holger

Stockholm University, Faculty of Science, Department of Physics.

2010 (English)Doctoral thesis, comprehensive summary (Other academic)

Abstract [en]

Biomimetic chemistry is directed towards the simulation of enzymatic reactivity with synthetic analogues. In this thesis a quantum chemical method has been employed to study the mechanism of highly reactive iron-oxo complexes involved in oxygenation and chlorination of organic substrates. The aim of this research is to gain greater understanding for the reactivity paradigm of the iron-oxo group.

One reaction deals with the conversion of cyclohexane into adipic acid, a key chemical in industrial chemistry, catalyzed by an iron(II)-porphyrin complex in the presence of dioxygen. This process constitutes a ’green’ alternative to conventional adipic acid production, and is thus of great interest to synthetic chemistry. Another reaction investigated herein regards the selective chlorination observed for a new group of non-heme iron enzymes. With help of theoretical modeling it was possible to propose a mechanism that explains the observed selectivity. It is furthermore demonstrated how a biomimetic iron complex simulates the enzymatic reactivity by a different mechanism.

Other topics covered in this thesis regard the structure-reactivity relationship of a binuclear iron complex and the intradiol C-C bond cleavage of catechol catalyzed by an iron(III) complex.

Public defence

Opponent

Kaupp, Martin

Supervisors

Blomberg, Margareta R. A.

Stockholm University, Faculty of Science, Department of Physics.

Siegbahn, Per E. M.

Stockholm University, Faculty of Science, Department of Physics.

Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Accepted. Paper 3: Submitted.Available from: 2010-04-08 Created: 2010-03-31 Last updated: 2010-04-07Bibliographically approved